Please help... loss of power, running "flat"

Good morning all, I have been having an issue with my ITA 240SX for about 1.5 years now that I just can't seem to pin down. It made for a very discouraging race weekend...
The car runs ok for the first few laps of a session, but then it's almost like a switch (or a bad sensor that doesn't like heat). The car looses power, and the sound of the exhaust changes to a flat (almost splatty) tone.
I have a new (last september) stock radiator, summit oil cooler, stock water temp gauge (which never shows above normal) and oil pressure gauge (about 50psi when I'm above 2500rpm). I don't have an oil temp gauge (will install one before next race weekend)
I have both a stock auto trans ECU, and a chipped manual trans ECU (problem happens with both ECU's)
I have installed a crude heat shield to keep exhaust heat away from air filter (and have a heat-tape wrapped Injen cold air intake), and monitor incoming air temp, which only went above 75F when I was right on someone's bumper.
Things I know:
fuel pressure is good all the way through the rpm range
air/fuel is 11.5 - 12.5 all through the rpm range
(both of the above from a dyno session last october, which showed VERY dissapointing numbers)
water doesn't seem to be getting too hot (unless sensor or gauge is bad, but sensor was replaced last september when I did the radiator) also using a 160F thermostat
using stock heat-range plugs, with an MSD coil
I took the distributor dust cover off at the track and the disc and sensor underneath were clean (I'm thinking about replacing the sensor just because)

Things I don't know:
EVERY other 240 I've seen in person or online ALWAYS has an oversized aluminum radiator... do I need one? If so, who/where do I get it from?
Is this a spark or heat issue? Anyone ever run into a similar problem?

As you guys know, this car is FAST when running right... I got down to 1:20.7 at Nelson Ledges in my rookie year (driving like crap). I know that I'm cornering much faster now, but I just watch everyone pass me by on both straights and this past weekend, couldn't get below 1:22.

Hopefully no Mazda guys are reading, but on the back straight this past weekend, my uncle passed me like I was standing still (in an ITA RX7!!!)

Any ideas???
Thanks,
Mike

What plugs are you running?

This past weekend was Denso 3135 (I don't remember the heat range info on the side of the porcelain)
I have also previously run NGK in this heat range, which is 6 in their part number, I think, and one colder heat range

Car has two water temp sensors, one for the gauge, one for the ECU. Also, I "think" there's a safe mode for water temp. I don't remember all that Jim Wolf Tech told me when I had them do mine.

We also had a fuel pump crap out. Seemed to run fine except when you really put a load on, would run up to 6k in first few gears but not 5th. New pump fixed it.

To start with the 3135 crosses to a 5 range NGK which is way too hot for continued high speed use. Try going to a 7 or 8 range NGK or I use a C61 champion race plugs in these.. The feeling of engine going soft is consistant with plugs that are to hot. Fuelpump going soft is possible but you indicated your mixture was consistantly ok. Start with plugs and go to the chassis dyno. A faulty coolant sensor can also be the issue but again you should see that in the mixture gauge.

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Good morning all, I have been having an issue with my ITA 240SX for about 1.5 years now that I just can't seem to pin down. It made for a very discouraging race weekend...
The car runs ok for the first few laps of a session, but then it's almost like a switch (or a bad sensor that doesn't like heat). The car looses power, and the sound of the exhaust changes to a flat (almost splatty) tone.
I have a new (last september) stock radiator, summit oil cooler, stock water temp gauge (which never shows above normal) and oil pressure gauge (about 50psi when I'm above 2500rpm). I don't have an oil temp gauge (will install one before next race weekend)
I have both a stock auto trans ECU, and a chipped manual trans ECU (problem happens with both ECU's)
I have installed a crude heat shield to keep exhaust heat away from air filter (and have a heat-tape wrapped Injen cold air intake), and monitor incoming air temp, which only went above 75F when I was right on someone's bumper.
Things I know:
fuel pressure is good all the way through the rpm range
air/fuel is 11.5 - 12.5 all through the rpm range
(both of the above from a dyno session last october, which showed VERY dissapointing numbers)
water doesn't seem to be getting too hot (unless sensor or gauge is bad, but sensor was replaced last september when I did the radiator) also using a 160F thermostat
using stock heat-range plugs, with an MSD coil
I took the distributor dust cover off at the track and the disc and sensor underneath were clean (I'm thinking about replacing the sensor just because)

Things I don't know:
EVERY other 240 I've seen in person or online ALWAYS has an oversized aluminum radiator... do I need one? If so, who/where do I get it from?
Is this a spark or heat issue? Anyone ever run into a similar problem?

As you guys know, this car is FAST when running right... I got down to 1:20.7 at Nelson Ledges in my rookie year (driving like crap). I know that I'm cornering much faster now, but I just watch everyone pass me by on both straights and this past weekend, couldn't get below 1:22.

Hopefully no Mazda guys are reading, but on the back straight this past weekend, my uncle passed me like I was standing still (in an ITA RX7!!!)

Any ideas???
Thanks,
Mike
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does the timing sound like it is off? Maybe a problem with the distributor or the distributor jumped a tooth on the crank gear. Both are common.

Check this thread/post. A lot of good info there.

http://itforum.improvedtouring.com/forums/...indpost&p=64511

PDM Racing has everything you should need for these cars. But Joe H. is the man. He knows way more than pretty much anyone on here about these cars.

Yes, I would get an oversized Aluminum Radiator. I can't believe you're not overheating it with a stock radiator.

http://www.pdm-racing.com/products/cooling.html

steve

Thanks guys...

I thought about the distributor jumping a tooth, but no...
Should I get the crank angle sensor and replace that, or just find a whole distributor to try?

also has a brand new oil pump gear and spindle (found out the hard way that those two are wear items)

Quote:

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Thanks guys...

I thought about the distributor jumping a tooth, but no...
Should I get the crank angle sensor and replace that, or just find a whole distributor to try?

also has a brand new oil pump gear and spindle (found out the hard way that those two are wear items)
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I would just buy a whole distributor. A spare distributor and coil should be a must to have on hand. So, buy one and keep it as a good known spare if it doesn't end up needing replacement.

Not that it seems like you're having fuel problems, but if I was running one of these cars and didn't know if any of the fuel system was replaced I would replace all of it. Fuel pump, filter, FPR, and injectors (send em to be cleaned). Cause if you haven't had issues yet you will, and probably soon.

s

Fuel pump & fpr were replaced last spring, and the injectors were sent out for clean and flowtest last november. Fuel filter gets changed every spring with the "all fluid change"
wow... I've gone down so many paths to try and find this, I'm starting to forget all the stuff I've done to the car (probably better that way, if I forget I did it, I'll forget the money too!)

Wow, you could spend a fortune buying parts, I am completely serious about the heat range on those plugs being wrong and a large part of the problem. The stock rad will handle 200hp and a 90 degree day no issue. Most of the reason people say it won't is they try to run a lot of boost in the sr20s and they overheat. Don't waste a bunch of money till you change the plugs. We gapped the plugs wrong on my RS motor once and knocked 15hp out of the thing right away.

Edit: one other thing to add. Check the grounds on the engine...Front of the intake manifold passenger side and rear of head driverside. Grounds are critical on these engines. Also check the coil wire at the coil end of the wire. Most people leave these hanging and enough boucing around pulls them loose from the cap but not enough to just fall off.

Also pull your plugs and look at them under a magnifier or plug light. Check for signs of detonation and metal transfer...little balling on the electrodes..

Try emailing Brandon Bogart ( Brandon at bbracingusa dot com ) We haven't had one with those exact symptoms since I've been with the team, but he might have an idea on where to go next.

All the above advice is great. Take one of Joe's comments to heart, you can spend a ton of money chasing this. Without data you are just another person with an opinion! Spend a little money on testing to find out what it is. You spoke of the fuel mixture from your dyno session. Most chassis dyno work doesn't run long enough to get to the point where you see the problem. Take the car to the dyno and explain what you are seeing, you may be able to make a couple passes in rapid succession to build heat, make the passes in 5th gear to build more heat, etc. This will help point you in the right direction. Cheaper than a wasted weekend!

The other option is to borrow, or buy if that is doable, a LM-1 wide band O2 sensor and see if the mixture changes when it falls on it's face. Install it in the car where you can see it during the session.

Two cars I have seen act like this, one was my car due to heavy floats causing a very rich mixture at high end. The other is a friends 240 when he had a leaking power brake booster. Ran fine at lower RPM, but at higher RPM it would suck past the leak and lean out. Very lucky to not blow that one up.

Hope this helps, good luck!

Mike

I think initially I'll get the plugs, and also heat-wrap the exhaust header
I'll wait on the radiator, because unless the sensor is bad, I'm not overheating (before I put the new radiator in, I used to hear the water boiling in the radiator after a session on a hot day, but not since) Also going to add oil temp gauge, so I'll check that and see what both temps look like
The dyno I went to was part of a larger complex of buildings, I'll try to schedule on a saturday that is supposed to be warm, and run a few laps around the parking lot first. I'll let them know I'd like to do multiple pulls quickly to get the heat up (maybe tell them I only want to use my cooling fan, not place their big one in front of the car???)
Thanks,
Mike

Another issue seen on the 240's is heat affecting the distributer causing the timing to jump around. This may explain the flat power after running a while. Some of us wrap or shield the distributer.

Good moning all,
I just wanted to get online and say... "Thank you!"
I wrapped my header, put a summit starter heat shield around my distributor and went to heat range 7 plugs. The opportunity arose to go to a test/funday on friday, and WOW. Big difference from the race weekend at the end of april. It still seemed like it was dropping off slightly, but nowhere near what it was before. I think I'll get some heat range 8 plugs and do some trial-and-error next time out to the track and see if there's a difference.

Again, thanks guys